Popularity is an Aspiration in The Sims 2. Popularity Sims want to make friends as many people as possible. They like to meet somebody new, befriend them, make best friends with them, and eventually become BFF[TS2:FT] with them. This is a neverending cycle of friendship as they tend to want to be friends with anyone they've met. They also love to throw great parties, join Greek house[TS2:U], and have a good Reputation[TS2:AL].
Besides the good friendship development, some Popularity Sims also have bad sides. They tend to want to win a fight against their enemies.
Local Hero / Local Heroine
Mr. Popularity / Ms. Popularity
Man About Town / Woman About Town
One of the Gang
Wants & Fears
The wants are the same for all age groups, except that young adult Sims will often have wants to become the Big Sim on Campus and to join a Greek house. Popularity Sims will often roll wants to become friends with Sims they have recently met, even though they do not know them well.
It is not recommended for a Popularity Sim to have children, unless you want a challenge; as children and toddlers fear having parties and Popularity Sims want to have parties.
Being a witch or warlock can be a good thing for Popularity sims as they have wants to make friends and have lots of best friends; powerful good aligned witches can use magic to make friends - this could stack with their 'Fast Friends' Aspiration benefit. They can throw better parties as well, by casting spells to force other sims to accept the next five interactions.